1. Field of the Invention
Exemplary embodiments of the present invention relate to an apparatus and method for transmitting and receiving data in a wireless communication system; and, more particularly, to an apparatus and method for transmitting and receiving data according to a final back off time by applying a beamforming weight to a subchannel including an optimal channel environment in a wireless communication system.
2. Description of Related Art
A wireless communication system wirelessly connects a plurality of stations in a wireless network and enables them to transmit and to receive data through a wireless link. That is, the plurality of stations load data on a carrier frequency and transmit the data through air. Many wireless networks have been introduced, for example, a local area network (LAN), a personal area network (PAN), and a metropolitan area network (MAN).
Lately, such a wireless communication system has been adapted an orthogonal frequency division multiplexing (OFDM) technology and a multi-antenna technology such as a multiple-input and multiple-output (MIMO) technology. The OFDM technology divides data requiring a high transmit rate into a plurality of data with a low transmit rate and transmits the plurality of data with a low transmit rate at the same time using a plurality of subcarriers.
The MIMO technology improves a data transmission/reception efficiency using multiple transmission antennas and multiple reception antennas. Since a next generation mobile system or a next generation wireless communication system requires transmitting mess amount of data with a high transmit rate, many studies have been made to develop a method for transmitting and receiving data using the MIMO technology. Such a MIMO technology can divide a channel to a plurality of independent channels such as spatial layers or streams according to the number of transmission antennas and reception antennas.
A MIMO system has been used a spatial multiplexing scheme, a spatial diversity scheme, and a beamforming scheme as a data transmission/reception method. The spatial diversity scheme is a technology for transmitting data at a high transmit rate without increasing a system bandwidth by transmitting different data at the same time using multiple transmission antennas. The spatial diversity scheme allows a transmitter to select an optimal path among multiple paths and to transmit data through the selected optimal path to a receiver.
The beamforming scheme is a technology for arranging a plurality of antennas at a regular gap and transmitting the same data by multiplying the data with a weight vector of each antenna. The beamforming scheme advantageously reduces interference to a mobile station located on a direction different from a beam direction of an antenna and increases a signal to interference plus noise ratio (SINR) of a target mobile station with the same power at the same time. However, the beamforming scheme requires association of a transmitter and a plurality of receivers when the transmitter transmits the plurality of receivers. If the association process repeats to transmit data between the transmitter and the receivers, overall time and resources will be wasted.